1. Field of the Invention
This invention relates to surgical instruments such as, for example, forceps and scissors, and more particularly to surgical instruments ideally adapted for operations to be performed under an endoscopic surgery.
2. Description of the Prior Art
A forceps so constructed as to effect remote control of a grasping mechanism disposed at the leading end thereof with a manipulating part disposed on the basal end side thereof has been known (JA-Y2-02-46,327, JA-U-05-76,413, etc.). Specifically, this forceps is provided at the leading end thereof with a grasping mechanism consisting of a pair of open-close claw member and at the basal end part of a transmission shaft connected to the grasping mechanism with claw manipulating means consisting of a stationary grasping part and a rotary grasping part rotatable toward and away from the stationary grasping part, whereby a rotation of the rotary grasping part induces traction of a transmitting lever built in the transmission shaft in the longitudinal direction so as to open or close the claw member. Either of the stationary grasping member and the rotary grasping member is provided with a ratchet member and the remaining member with an engaging member adapted to be meshed with the teeth of the ratchet member. In this mechanism by adjusting the position of engagement between the ratchet member and the engaging member, the opening angle of the rotary grasping part relative to the stationary grasping member is set as desired and, consequently, the opening angle of the two claw members of the grasping mechanism is fixed.
Incidentally, regarding the excision of the appendix and the gallbladder, the operation performed under an endoscopic surgery and obviating the necessity for laparotomy has been attracting attention in recent years as a prospective alternative to the conventional laparotomy. This operation under an endoscopic surgery is implemented by inserting four trocars, for example, through the abdominal wall into the abdominal cavity, displaying on a monitor screen the image of the interior of the abdominal cavity with the aid of a miniature camera inserted via one of the trocars, and enabling the surgeon to study the image on the screen and perform a desired surgical treatment by manipulating suitably a forceps, a scissors, and an electric scalpel inserted via the other trocars.
In this operation under an endoscopic surgery, the trocars which are straight tubes are inserted through the abdominal wall and fixed thereto. For the sake of protecting the tissue of the pierced part, the angle which the trocars form with the abdominal wall cannot be substantially varied. As a result, the forceps, the scissors, and the electric scalpel are allowed to produce surgical treatments in only limited areas.
For the solution of this problem, it has been proposed to enlarge the area to be covered by the grasping mechanism at the leading end of the forceps by adapting the forceps to produce a bend or a curve in the leading end part of the elongate main body (transmission shaft) thereof after the forceps has been inserted through the trocar thereby allowing the bend or the curve to be utilized in combination with the rotation of the forceps.
The conventional forceps described above, however, premises use of a rectilinear transmission shaft defying deformation and essentially requires a ratchet mechanism (a ratchet member and an engaging member) for fixing the opening angle of the two claw members of the grasping mechanism to be disposed in the handle manipulating part near the operator's hand. If the transmission shaft is adapted to produce a bend or a curve the conventional forceps will entail the following problem.
In the first place, when the transmission shaft is bent or curved, the tension of the transmitting lever built in the transmission shaft is proportionately varied and the opening angle of the two claw members and the grasping force of the forceps are inevitably varied possibly to the extent of hindering relevant surgical treatments. This problem is not limited to the case of bending or curving the transmission shaft. It originates also in the elongation of the transmitting level and the play and the backlash of the claw manipulating means owing to changes in ambient conditions and material characteristics. In the second place, since the handle manipulating part is provided with a mechanism for fixing the opening angle of the forceps and a leaf spring for urging the rotary grasping part, these accessorial components possibly obstruct the manipulation of the handle and jeopardize the convenience of manipulation and, at the same time, complicate the construction of the forceps.